Production of unsaturated fatty acids



Patented July 10. 1934 PRODUCTION OF UNSATURATED FATTY ACID MartinLuther and Hans Klein, Mannheim, Germany.

assignors to I. G.

Farbenindustrie Aktiengesellschaft, Frankfort on the Main, Germany, acorporation of Germany No Drawing. Application May 29, 1929, Serial No.367,116. In Germany June 4, 1928 Claims. (Cl. 260-119) The presentinvention relates to the production of unsaturated fatty acids.

The oxidation of paraflin hydrocarbons, waxes and the like by means ofgases containing oxy- 5 gen, at an elevated temperature furnishesproducts which contain, inter alia, large amounts of dark colored acidcompounds and conversion products thereof, both of which are insolublein petroleum ether. For many purposes, such for example as soapmaking,it is essential that these admixtures should be eliminated from theoxidation products.

We have now found that valuable mixtures of unsaturated and saturatedcarboxylic acids can be, obtained from the oxidation products bysubjecting the crude oxidation product to distillation. For example, thecrude oxidation product may be distilled, preferably under reducedpressure, the operation proceeding smoothly and the unsaturated andsaturated acids and the like dis tilling over and leaving only acomparatively small residue. The heat of distillation effects anextensive conversion of the hydroxy carboxylic acids into unsaturatedfatty acids, so that the 5 distillate no longer contains any hydroxycarboxylic acids and is suitable for direct use for many purposes. Ifesters of the hydroxy carboxylic acids and of saturated fatty acids bepresent in the crude oxidation products a considerable portion of theesters of the latter and those of the unsaturated acids corresponding tothe aforesaid esters of hydroxy carboxylic acids is found in thedistillate. If desirable the distillation may be repeated one or moretimes. The losses of material during the distillation are very slight,and above all, there is no appreciable splitting ofi of carbon dioxidefrom the acids, in

contrast to the results obtained in a distillationof pure hydroxycarboxylic acids after isolating 0 these acids from a crude oxidationproduct of the aforesaid nature. This is evident from the saponiflcationvalues of the products before and after distillation. Particularly inthis respect good results are obtained by applyin a current of carbondioxide during the distillation wherefore or after removingunsaponifiable materials, if such be present, the unsaturated acidsbeing thereby converted into the saturated state.

The operation may also be carried out with an acid product which hasbeen freed from unoxidized initial materials, for example by subjectingthe crude oxidation product to mechanical pressure or to sweating belowthe melting point of the acids present, or with the entire acid portionof the oxidation product, both 5 which materials will be referred to,for the sake ofbrevity, in the following as a pretreated oxidationproduct. Particularly good yields of unsaturated acids are obtained whenthe oxidation of the parafiin hydrocarbons, waxesandthe like 7 has beenperformed rather strongly, for example with the aid of catalysts, sincealso such pretreated product is not liable-to give the bad resultsobtainable" with pure hydroxy carboxylic acids stated above.

As a rule the distillation is preferably carried out in the presence ofa current of an inert gaseous agent, such as carbon dioxide or watervapor and the like.

The distillation is advantageously carried out rather quickly and withan addition of. steam. After the second distillation the distillates arepractically free from hydroxy carboxylic acids, and consist almostexclusively of valuable unsaturated fatty acids. For some purposes, suchas the preparation of solid edible fats, they may be subsequentlyhydrogenated. If desired, a catalyst may be employed in thedistillation, for example red phosphorus, sulphuric acid or metaloxides, but usually the employment thereof may be dispensed with, verygood results being obtainable without the use of a catalyst.

The following examples will further illustrate the nature of theinvention, but the invention is not restricted to these examples. Theparts are. by weight.

Example 1 500 parts of an oxidation product obtained from hard paraffinwax, with the acid value of 108, a saponification value of 205, andcontaining 2'7 per cent of acids insoluble in petroleum ether, aredistilled in a vacuum of 8 millimeters (mercury gauge) at 110 to 280 C.432 partsof distillate are obtained which has an acid value of 153, asaponification value of 200, and a content of only 5 per cent of acidsinsoluble in petroleum ether.

400 parts of the distillate are re-distilled, under 3 millimeterspressure and in an atmosphere of 110 CO2, whereupon 384 parts pass overat from 140 to 290 C. The distillate has an unaltered acid value of 153and a saponification value of 200, and contains only 2 per cent of acidsinsoluble in petroleum ether. The same procedure for the production ofunsaturated acids may be followed in the treatment of the oxidationproducts from Montan wax, beeswax, ozokerite and the like.

Example 2 100 parts of a crude oxidation product obtained from anoxidation of soft parafiin wax of brown coal tar and possessing an acidvalue of 108 and a saponification value of 205 are distilled at 15millimeters mercury gaugewhile passing through a current of steam andraising the temperature up to about 260 C. 90 parts of a practicallyanhydrous mixture of an acid product are obtained after fractionalcondensation, the product showing an acid value of 146 and asaponification value of 200. When carbon dioxide is employed in theplace of steam about the same yield with the same acid value is obtainedand the saponificatior. value is that of the initial material. Theprocess is similar when an oxidation product of liquid parafllnhydrocarbons or of Montan wax be employed.

What we claim is:

1. The process for the production of unsaturated fatty acids, whichcomprises subjecting to distillation, at a temperature between about 110and about 290 C. and at a pressure up to atmospheric pressure a crudeproduct containing a substantial proportion of long chain hydroxycarboxylic acids from the super-oxidation of difilcultly volatileparafiin hydrocarbons and waxes, thereby converting said long chainhydroxy-carboxylic acids into long chain unsaturated fatty acids.

2. The process for the production of unsatu-' rated fatty acids, whichcomprises subjecting to distillation, at a. temperature between about110 and about 290 C. and at a pressure up to atmospheric pressure acrude product containing a substantial proportion of long chain hydroxycarboxylic acids from the'super-oxidation of difficultly volatileparafiin hydrocarbons and waxes, while passing an inert gaseous agentthrough the reaction vessel, thereby converting said long chainhydroxy-carboxylic acids into long chain unsaturated fatty acids.

3. The process for the production of unsaturated fatty acids,whichcomprises subjecting to distillation, at a temperature betweenabout 110 and about 290 C. and at a pressure below atmospheric pressure,a crude product containing a substantial proportion of long chainhydroxy carboxylic acids from the super-oxidation of dimcultly volatileparaffin hydrocarbons and waxes, which crude product has been freed fromunoxidized initial materials thereby converting the said long chainhydroxy carboxylic acids into long chain unsaturated fatty acids.

4. The process for the production of unsaturated fatty acids, whichcomprises subjecting to distillation, at a temperature between about 110and about 280 C. and at a pressure of about 8 100 millimeters ofmercury, a crude super-oxidation product of hard paraffin wax, therebyconverting the long chain hydroxy carboxylic acids contained in saidsuper-oxidation product into long chain unsaturated fatty acids.

5. The process for the production of unsaturated fatty acids whichcomprises subjecting to distillation, at a temperature between about 110and about 260 C. and atv a pressure of about 15 millimeters of mercury,a crude oxidation prod- 110 uct from soft paraffin wax, while passing acurrent of steam through the distilling batch, thereby converting thelong chain hydroxy carboxylic acids contained in said oxidation'productinto long chain unsaturated fatty acids.

' MARTIN LUTHER.

HANS KLEIN.

